Diazotype light-sensitive materials



Patented Dec. 14, 1948 DIAZOTYPE LIGHT- SENSITIVE MATERIALS Derland Johnston, Evanston, Ill., assignor to Charles Bruning Company, Inc., New York, N. Y., a corporation of New York No Drawing. Application September 7,1945, Serial No. 615,084

Claims.

This invention relates to light-sensitive layers for diazotype prints, and more particularly to such layers containing light-sensitive diazo compounds which are characterized by having both abenzyloxy and an acylamino substituent in the aromatic ring to which the diazo group is attached.

Diazotyp printing is an established art and a variety of light-sensitive compounds are used therein. The light-sensitive layers are printed by irradiating with light through transparencies having designs blackedout or drawn thereon. In the exposed areas, the diazo compound is destroyed While in the dark or shadow areas, it is not destroyed. The print is developed by reaction with a so-called azo coupling component, such as, for instance, phloroglucinol. The development step results in the production of an azo dye.

In some processes, both the diazo compound and the coupling component are coated on a diazotype paper, and after printing, the coupling reaction is carried out by treatment with moisture or ammonia gas. .In another type of diazotype process, only the diazo compound is coated on the diazotype paper, and after the printing thereof, the azo component is applied to the paper as a solution in a solvent. In general, the latter type or one-component papers have agreater stability than the former or two-component papers. That is, they have better storage and keeping qualities than the two-component type papers. Generally, the one-component type papers give dark developed lines and better contrast between the lines and the background.

.As the diazotype printing art has developed, certain inherent drawbacks of the heretoforeproposedone-component papers have confronted the art. One such drawback is that solutions of the azo coupling components used tend to deteriorate and discolor upon long exposure to the oxygen of the atmosphere. One method'of mitigating this deterioration is to employ the am coupling compound in solution at a slightly alkaline, neutral or somewhat acid pH, wherein it is not rapidly oxidized. For this :purpose, diazo compounds which are sufficiently active to couplein a slightly alkaline, neutral or acdmedium are necessary.

Another drawback of the one-component type papers is that in the treatment with .a Iliquidsolution of a coupling component, there is a tendency for the lines to bleed, that is, to give a print which .is blurred as compared to the original. This might be due to the-solubility of the developed dye in thesolutionof the coupling component. It might-also bedue to the solubility of the diazo compound or an intermediate reaction product of the diazo compound with the coupling component in the solution of the coupling component.

In order that the developed diazotype print will have a good contrast between the printed outline and the background, the final azo dye should have a dark color and the background should be of a very light or white color and substantially free of discoloration. Discoloration of the background may be due to decomposition products of the diazo compound which was burned out in the printing process or to oxidation of the phenolic materials applied by the developing solution.

Among the diazo compounds proposed heretofore, those containing an acylamino in the 4- position and also lower alkyl ether group in the ring have achieved a degree of success When used -in light-sensitive diazotype layers. The introduction of large groups, such as aralkoxy groups, into the ring tends to make the compound practically insoluble in water. Good water solubility has been regarded as necessary for diazotype compounds, and compounds which do not have good water solubility have been regarded as unsuitable for practical diazotype printing purposes.

Diazo derivatives obtained by diazotizing a benzyloxy substituted aniline, upon development with an azo coupling component of the phloroglucinal type at a pH of 9 or lower, give dyes of relatively light color.

It has now been found, and surprisingly indeed, that clear diazotype prints of very sharp contrast can be made from new, aralkoXy-substltuted, light-sensitive diazo compounds which give a very dark or practically black colored dye with a coupling component, such as polyhydroxy or polyamino benzenes, at a pH of about 9 or lower.

.A highly advantageous characteristic of these light-sensitive compounds and developed diazotype prints obtained therewith is substantial absence of bleeding. This is associated with substantially complete printing out of the diazo compound, even at relatively rapid printing speeds in the present day type of diazotype printing machines which generally use near-ultraviolet light, and substantial absence of coupling of decomposed diazo compound with the undecomposed diazo compound.

The diazo compounds embodying the invention have a high coupling activity and couple with an azo coupling component, such as phloroglucinol, practically instantaneously even at a pH of 9 or lower. These diazo compounds have a relatively low solubility in the liquid developer solution which may be reflected in the lack of any tendency for the diazo compound, or intermediate or final reaction products thereof with the coupling component, to bleed when being developed. The developed image remains very sharp and accurate reproductions or copies of a desired subject matter can be made very readily.

Diazotype prints obtained by means of compounds of the invention range in color from black to very dark red. With the new diazo compounds, it is possible to obtain sharp dark lines from transparencies having black pencil or black ink lines, so that the reproduction substantially duplicates the original drawing or subject matter in all particulars.

The diazo compounds of the present invention are derived from anilines having the following general formula:

in which X-- is an acylamino radical selected from the group consisting of Specific compounds which come within the scope of th above general formula are, for instance,

4 2,5-di-benzyloxyl-acetamido-aniline, 2,5-di-benzyloxy-4-formamido-aniline, 2,5-di-benzyloxy-4-propionamido-aniline, 2,5-di-benzyloxy-4-butyramido-aniline, 2,5-di-benzyloxy-4-iso-butyramido-aniline, 2,5-di-benzyloxy-4-benzamido-aniline, 2,5-di-benzyloxy-4-phenylacetamido-aniline, 2,5-di-benzyloxy-4-methoxyf-ormamidoaniline, 2,5-di-benzyloxy-4-ethoxyformanido-aniline, 2,5-di-benzyloXy-4-propoxyformanido aniline, 2,5-di-benzyloxy-4-succinimidoaniline,

The diazo derivative may be, for example, the chloride, or salts of any other suitable anion, or the metal salt complexes therewith, such as the zinc chloride complex of the diazo chloride derivative.

These compounds may be prepared from hydroquinone as a starting material. One hydroxyl may be etherified with a benzyl group by treatment with the stoichiometric amount for one ether group of benzyl chloride in the presence of caustic, and then the second hydroxyl group may be etherified with a similar group by a similar procedure. Both hydroxyl groups may be etherified simultaneously, for instance, by treatment with an excess of the benzyl chloride required for the two ether groups. The resulting di-etherified compound may be mononitrated by treatment with nitric acid in the presence of acetic acid as the solvent.

. The mono-nitro compound obtained may be reduced to the corresponding aniline, for instance, by treatment with finely divided iron and hydrochloric' acid in a boiling alcohol solution, or by catalytic hydrogenation under pressure, The resulting substituted aniline may be treated with an acylating agent to form the corresponding amido or imido substituted compound. The acylated compound may then be nitrated again by the above procedure. This nitro group is believed to enter into the ring at the position para to the acylated amino group in View of the para directing influence of the amido group plus the ortho directing influence of the benzyloxy group which is in a meta position relative to the acylated amino group. The resulting nitro compound may be reduc'ed by the above discussed procedures to the corresponding 2,5-di-etherified aniline containing a benzyloxy group in the 5-position and an acylated amino group in the 4-position. This aniline may be diazotized by dissolving in a solution such as hydrochloric acid and treating with sodium nitrite, or nitrous acid. The resulting diazo compound may be precipitated by forming a metal salt complex thereof, such as a zinc chloride complex of the diazo chloride derivative. Such complexes are relatively insoluble in water. v

In order to illustrate the invention and point out some of the advantages thereof, the following specific examples are included. However, these are not to be construed as limitations 'of the invention as otherwise disclosed herein.

Ewample 1' grams of hydroquinone was mixed with 228 cc. of benzyl chloride and 1820 cc. of commercial denatured alcohol and the solution was refluxed. The heating was stopped, and a cool solution of 82 grams of sodium hydroxide in 136 cc. of water was added in small portions through the reflux condenser, while agitating the reaction mass. Refluxing was continued for three hours thereafter. Hydroquinone dibenzyl ether was obtained by working up the reaction mass. 100 grams of this ether, dissolved in glacial acetic acid, was slowly treated with 27 cc. of concentrated nitricacid and yielded 2,5-di-benzyloxy nitrobenzene which wasreduced to the corresponding aniline by treatment with iron powder and hydrochloric acid in warm alcohol, This aniline was dispersed in glacial acetic anhydride to give the corresponding ac'etanilide. The acetylatde compound was mononitrated and the nitro compound reduced to the corresponding aniline by the procedures described above. The product obtained was a gray-white solid, melting point 105 to 106 C. This aniline was dispersed in concentrated hydrochloric acid solution and then diazotized by treatment with aqueous sodium nitrite solution. After the excess nitrous acid was destroyed by adding sulfamic acid, the reaction mass was-treated with aqueous zinc chloride solution and a light yellow colored zinc chloride complex of the diazo chloride derivative of the above aniine was obtained as a precipitate. The product is believed to be a diazo derivative of 2,5-di-benzyloxy-4-acetamidoaniline.

One gram of this zinc chloride diazo complex was dissolved in 100 cc. water. l grams of citric acid and 2 grams of boric acid were added thereto, with agitation. The resulting solution was filtered and applied in a thin film to sized paper. The coated paper was dried in the dark. The coating and drying operation was repeated until a test portion'ofthe paper gave a dye image of desired density upon development with an azo coupling component, such as phloroglucinol.

The resulting coated paper was printed by light from a standard diazotype printing machine with a transparency having a drawing thereon for seconds. The shaded portions retained the yellow color of the light-sensitive coating and the irradiated portions printed out substantially to the white color of the original paper.

The printed diazotype paper was then developed by treatment in a commercial semi-dry developing machine using a liquid developer or" the following composition:

Grams Phloroglucinol 0.4 'Sodium'formate 8.0 Sodium benzoate 3.0 Thiourea 2.0 Wetting agent (sold under the trade name Santomerse D) 01 l/Vater, "con 100 The pH of this developing solution is '7.

A similar sheet of diazotypepaper Was printed as above and developed with a developerof'the following composition:

The above composition, plus 0.4 gram of tartaric acid. This developer had a pH of 5.5.

Example 2 2,5-benzyloxy aniline was prepared in accordance with the procedures of Example 1. 32 grams thereof was dissolved in benzene with the aid of heat and refluxing. 13 grams of succinic anhydride was dissolved in cc. of hot benzene and added to the aniline solution. The resulting mixture, or mass, was heated with refluxing for two hours. Wool-like crystals precipitated from the hot solution. The solution was cooled, filtered, and Washed with benzene and then with alcohol. The resulting product, 2-succinimido 1,4 dibenzyloxy benzene, was mono-nitrated to give 4-succinylimino 2,5-di-benzyloxy nitrobenzene. This nitro compound was then reduced to the corresponding aniline by means of powdered iron and hydrochloric acid in a hot commercial denatured alcohol solution. This substituted aniline is a white solid which melts at 168 to 170 C. It was diazotized following the procedure of Example 1 and recovered as the zinc chloride complex, which was a yellow-brown powder. This product is believed to be a diazo derivative of 2,5- di-benzyloxy-4-succinimido aniline.

Following the procedure of Example 1, diazotype sheets were made up from this diazo compound zinc chloride complex, printed and developed. The printed sheets developed with either type of developer showed sharp contrasting substantially black lines on a substantially white background which had a faint bluish tint. The image was accurately reproduced and there was no bleeding or blurring of the lines. The developed sheets were allowed to stand open to the atmosphere of a room and ordinary daylight for several months. There was no sign of'deterioration of either the background or printed image.

In the preparation of the acidamido intermediate compounds, the acyl group may be introduced into the amine group with a variety of acid derivatives, such as the acid anhydride or chloride, or in some cases even the free acids themselves. The benzamido compound can be prepared by treatment with the benzoyl chloride, in an alkaline solution. The formamido compound can be prepared by condensing the benzyloxy aniline with formic acid in boiling benzene.

The diazo compounds of the invention have a relatively low water solubility. It is possible by repeated coating and drying to produce lightsensitive layers containing sufiicient concentration of the diazo compound to give the desired intensity of printed and developed image. By using a warm solution, fewer coating and drying steps are required. It is more advantageous, however, to use a coating solution of the diazo compound in an aqueous solvent containing an alcohol or a ketone, such as ethanol, methanol, or acetone. It is possible to dissolve the diazo compound in commercial grades of ethanol, methanol; and acetone and use these as coatin solutions, preferably by diluting with water. If the solution is applied to the paper base which is somewhat porous, it may be desirous to incorporate, into the solution, various film forming materials such as dextrine, gelatine, gum arabic, gum tragacanth, or the like.

The new diazo materials develop readily with known developers, even at a pH of about 5 with some. Though the new compounds are especially suitable for the one component diazotype papers, they could be used in two-component papers of the powder type which are developed with moisture.

From the preceding description of the invention, it will be apparent that diazo compounds and light-sensitive layers containing such compounds having highly desirable properties have been produced. It will be understood, of course, that the compounds, the method of preparation and the development of the light-sensitive layers may be 7 modified considerably without departing from the invention.

I claim: 1..A light-sensitive diazotype material, comprising a light-sensitive diazo derivative of a compound having the general formula:

H-C-H t XG-NH:

t lat-H in which X is an acylamino-radical selected from the group consisting of formamido, acetamido, propionamido, butyramido, benzamido, phenylacetamido, methoxyformamido, ethoxyformamido, propoxyformamido and succinimido.

8 3. As a new product, a supporting base and light-sensitive layer thereon containing a lightsensivtive diazo derivative of a compound having the general formula:

I! 4. As a new product, a supporting base and a light-sensitive layer thereon containing a lightsensitive diazo derivative of a compound having the general formula:

H 40 0 H O HQC-O- -Iv-ONHI 5. As a new product, a supporting base and a light-sensitive layer thereon containing a lightsensitive diazo derivative of a compound having the general formula:

DERLAND J QHNSTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,816,989 Schmidt et a1 Aug. 4, 1931 2,113,944 Leuch Apr. 12, 1938 2,198,827 Leuch Apr. 30, 1940 2,215,739 Leuch Sept. 24, 1940 2,326,782 Jacobus Aug. 17, 1943 Certificate of Correction Patent No. 2,456,514. December 14, 1948. DERLAND JOHNSTON It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 3, line 55, left-hand portion of the formula, for

column 5, line 9, for acetylatde read acetylated; line 21, for aniine read aniline; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 12th day of April, A. D. 1949.

THOMAS F. MURPHY,

Assistant G'ommissioner of Patents. 

